sewage (black water) system
The existing sanitary system installed in the Fir is a vacuum based system (like that on an airplane). The basic system has a vacuum pump that maintains negative pressure between the black water tank and the toilets. When you "flush" the toilet, the valve opens and everything in the bowl get sucked away. I think you could flush a sweater down these toilets. The toilets use very little water. The toilets themselves are similar to residential toilets in size (not the little plastic toilets fitted to some boats). In general, we would like to keep the existing system. However, we need to move the processing center and piping for a vacuum system is fairly particular so this remains to be seen.
When Fir was last operated by the Coast Guard, sewage was collected in a large tank and occasionally pumped overboard.
It is no longer acceptable to pump effluent overboard. The solutions are to hold sewage in a tank and pump it out at marinas or add a processing plant that digests effluent to the point where it can be pumped overboard.
The Coast Guard regulations cover three types of sanitary systems. Type I relates to vessels much smaller than Fir. Fir can utilize either Type II or Type III MSDs. In Type II, the waste is either chemically or biologically treated prior to discharge and must meet limits of no more than 200 fecal coliforms per 100 milliliters and no more than 150 milligrams per liter of suspended solids. Type III MSDs stores waste and does not treat the effluent. The waste is pumped out later and treated in an onshore system or discharged outside U.S. waters.